In Fig. REF  we plot the number density field in our baseline simulation
Run-Base (left column of panels) and our model Run-Sym (right column of panels),
which assume asymmetric and isotropic blue supergiant progenitor stellar winds, respectively.
The dashed green contour is the tangential discontinuity, where blue supergiant and Wolf-Rayet
stellar winds are in equal proportions (\(Q=0.5\) ). Solid black and dashed-dotted red contours
trace \(v_{\phi }\)  and \(B_{\phi }\) , respectively, and the white cross marks the position of the star.
The model Run-Sym obviously generates a spherical nebula (Fig. REF d,f)
by fast-wind-slow-wind collision, as modelled in the work of [1]}.
In model Run-Base the asymmetric blue wind is expelled as a torus of outflowing material,
see the studies of [2]} and [3]},
respectively, onto which stellar rotation and a Parker wind is superposed
(Fig. REF a).
Both models have no phase transition, therefore, the Wolf-Rayet stellar wind
directly interacts with the luminous blue supergiant stellar wind.
The initial spherically-symmetric stellar wind of Run-Base is channelled by its
surroundings and adopts a bipolar morphology (Fig. REF c,e).
One clearly sees magnetic dipoles in both the old slow and new fast winds,
whose field lines are compressed in the shell region.
Given the size of the nebula (\(\le 10\, \rm pc\) ), the asymmetric nebulae can
develop inside of the region bordered by the termination shock of the main-sequence
stellar wind bubble [1]}. These rings should therefore form
even in the context of the supersonic bulk motion of the driving blue supergiant star
(Fig. REF b,d,f).
This mechanism is therefore the MHD equivalent of the young aspherical Wolf-Rayet nebulae
of red supergiant stars of [5]}, this time in the context
of a blue supergiant ancestor.
